This application claims priority rights of and is based on Japanese patent applications respectively filed in the Japanese Patent Office as listed below, the entire contents of which are hereby incorporated by reference.
JPAP10-333074 filed on Nov. 24, 1998
JPAP10-346365 filed on Dec. 7, 1998
JPAP10-346334 filed on Dec. 7, 1998
JPAP10-346435 filed on Dec. 7, 1998
1. Field of the Invention
This invention generally relates to a method and apparatus for image forming, and more particularly to a method and apparatus for image forming in which cleaning and discharging operations are efficiently performed relative to an image carrying member, an intermediate transfer member, and associated members.
2. Discussion of the Background
In image forming apparatuses such as copying machines, facsimile machines, printers, etc., a large number of techniques have been introduced, relating to cleaning and discharging of members associated with an image forming operation involving usage of toner. In particular, cleaning and discharging are important in a full-color image forming apparatus which is provided with an intermediate transfer member in addition to a commonly-used image carrying member. In such a full-color image forming apparatus, primary and secondary transfer operations are in turn performed so as to transfer a plurality of mono-color-toner images separately formed on the image carrying member onto a transfer sheet at one time via the intermediate transfer member.
More specifically, the image carrying member and the intermediate transfer member are arranged to contact each other so as to perform a primary transfer operation for transferring each mono-color-toner image from the image carrying member to the intermediate transfer member. For this, the full-color image forming apparatus is provided with a charge applying member for applying a charge to the intermediate transfer member to generates an electric field which generates a force to help such primary transfer operation. After a number of times of the primary transfer operation, a plurality of mono-color-toner images are overlaid with precision as one full-color-toner image on the intermediate transfer member. Then, a secondary transfer operation is performed to transfer this full-color-toner image held on the intermediate transfer member onto a transfer sheet which is also in contact with the intermediate transfer member.
The above-described intermediate transfer member is often used in a belt shape or a drum shape. An intermediate transfer belt, for example, typically has a medium range of a volume resistivity from about 108 xcexa9cm to about 1011 xcexa9cm, which normally does not require operations for discharging the surface of the intermediate transfer belt. This helps the cost reduction.
In using such an intermediate transfer member having a medium range of volume resistivity, the surface of the intermediate transfer member is applied with a bias to perform the primary transfer operation and thus has a charge thereon. However, this charge will leak through members in contact with the rear surface of the intermediate transfer member and no charge will therefore remain on the surface of the intermediate transfer member in a relatively short time period after the application of the charge.
As a result, the intermediate transfer member has the voltage which is 0 and greatly different from the voltage of the toner image transferred through the primary transfer operation. Due to this voltage difference, toner particles forming the toner image, particularly the topmost-laid mono-color-toner image, are attracted to the surface of the intermediate transfer member. This results in a toner dispersion in which the toner particles are dispersed on the surface of the intermediate transfer member. Such a toner dispersion may badly cause a dirty background of an image, a blur of an image such as letters, and so forth and therefore make an image deteriorated in quality.
To avoid this problem, the image forming apparatus has used the intermediate transfer member which has a high volume resistivity of about 1013 xcexa9cm. In using the intermediate transfer member having the high volume resistivity, the surface of the intermediate transfer member charges during the primary transfer operation due to an occurrence of discharge from the image carrying member and thus increases the voltage on the surface. Because of the high volume resistivity, the charge on the surface of the intermediate transfer member will not leak through the members in contact with the rear surface of the intermediate transfer member. Thereby, the difference of voltages between the intermediate transfer member and the toner image held on the intermediate transfer member is made relatively smaller. This helps to prevent the above-described toner dispersion.
In this case using the intermediate transfer member having the high volume resistivity, or the volume resistivity of at least 1011 xcexa9cm, the charge will remain on the surface of the intermediate transfer member till the time when the next primary transfer operation starts. This makes it difficult to generate the same electric field as made during the previous primary transfer operation. In this case, accordingly, the charge remaining on the surface of the intermediate transfer member need to be discharged before starting the next primary transfer operation.
In addition, when a transfer sheet is jammed during the image forming operation in the image forming apparatus, the toner image held on the intermediate transfer member may pass a region where the secondary transfer operation is conducted, without being actually transferred onto a transfer sheet. This toner image needs, of course, to be removed before the next toner image is formed on the intermediate transfer member. However, a common cleaning member such as a cleaning blade alone cannot sufficiently remove the toner because the full-color image forming apparatus uses a relatively large amount of toner during one time of the image forming process.
Conventionally, a corona charger is widely used as a non-contact-type discharging member for discharging the image carrying member and other members associated with the image forming process in an image forming apparatus. Such a non-contact type of discharging member typically generates ozone during discharging, which is undesired from the environmental aspect. In addition, the discharging member needs an application of discharging bias which is generated from an expensive high voltage AC (alternating current) power source. This increase a manufacturing cost.
In addition, the above-described intermediate transfer member having a relatively high volume resistivity changes its volume resistivity in accordance with various environmental factors such as temperature, humidity, and so forth. The intermediate transfer member also changes a charger level on the surface thereof in accordance with a number of layers of mono-color toner image. With these changes, if the discharging bias is not variable, the discharging operation may not sufficiently be performed, causing a reduction of efficiency of the primary transfer operation.
As for the cleaning in the full-color image forming apparatus, it is required a relatively high level of cleaning performance, as described above. Conventionally, this is achieved by pressing the cleaning member relative to the intermediate transfer member. However, since the intermediate transfer member is rotating, the adjustment of pressure by the cleaning member has a relatively narrow margin and therefore it cannot be adjusted in a satisfactory manner.
In addition, the above-described discharging operation is needed to be performed relative to a transfer sheet carrying member as well as the intermediate transfer member. The transfer sheet carrying member carries a transfer sheet having a toner image transferred from the intermediate transfer member through the secondary transfer operation. During the secondary transfer operation, the transfer sheet carrying member is commonly applied with a bias to help the performance of the secondary transfer operation. This bias may remain on the transfer sheet carrying member after the secondary transfer operation and interferes the generation of the electric field for the next secondary transfer operation, resulting in an inferior image quality. Such a charge problem on the transfer sheet carrying member is addressed by employing a non-contact-type discharging member which involves an ozone problem.
The present application relates to a novel image forming apparatus which includes an image carrying member, an intermediate transfer member, a charging member, a transfer mechanism, a discharging member, a direct current voltage source, and a direct current voltage controller. The image carrying member rotates and carries a toner image on a rotating surface thereof. The intermediate transfer member is deposited at a position facing and in contact with the image carrying member, rotates and receives the toner image from the image carrying member during a first transfer operation. The charging member applies a charge to the intermediate transfer member to cause an electric field around a region where the image carrying member and the intermediate transfer member contact with each other, where the electric field generates a force for initiating the first transfer operation. The transfer mechanism performs a second transfer operation for transferring the toner image from the intermediate transfer member to a transfer sheet. The discharging member performs a discharging operation for discharging the charge remaining on the intermediate transfer member with contacting the intermediate transfer member after a completion of the second transfer operation. The direct current voltage source applies a direct current voltage to the discharging member to cause the discharging member to perform the discharging operation. The direct current voltage controller controls the direct current voltage in accordance with a volume resistivity of the intermediate transfer member.
The above-mentioned volume resistivity of the intermediate transfer member may be in a range of about 1011 xcexa9cm to about 1014 xcexa9cm, or in a range of about 1012 xcexa9cm to about 1013 xcexa9cm.
The present application also relates to a novel method of image forming which includes the steps of providing, rotating, charge applying, performing, direct current voltage applying, and controlling. The providing step provides a toner image to an carrying member for rotating and carrying the toner image on a rotating surface thereof. The rotating step rotates an intermediate transfer member which is arranged at a position facing and in contact with the image carrying member. The charge applying step applies a charge to the intermediate transfer member to cause an electric field around a region where the image carrying member and the intermediate transfer member contact with each other so that the electric field generates a force for initiating a first transfer operation for transferring the toner image from the image carrying member to the intermediate transfer member. The performing step performs a second transfer operation for transferring the toner image from the intermediate transfer member to a transfer sheet. The direct current voltage applying step applies a direct current voltage to the discharging member to cause the discharging member which discharges the charge remaining on the intermediate transfer member with contacting the intermediate transfer member after a completion of the second transfer operation. The controlling step controls the direct current voltage in accordance with a volume resistivity of the intermediate transfer member.
Further, the present application relates to another novel image forming apparatus which includes an image carrying member, an intermediate transfer member, a charging member, a transfer mechanism, a discharging member, a direct current voltage source, a voltage detect sensor, and a direct current voltage controller. The image carrying member rotates and carries a toner image on a rotating surface thereof. The intermediate transfer member which is deposited at a position facing and in contact with the image carrying member, rotates and receives the toner image from the image carrying member during a first transfer operation. The charging member applies a charge to the intermediate transfer member to cause an electric field around a region where the image carrying member and the intermediate transfer member contact with each other, where the electric field generates a force for initiating the first transfer operation. The transfer mechanism performs a second transfer operation for transferring the toner image from the intermediate transfer member to a transfer sheet. The discharging member performs a discharging operation for discharging the charge remaining on the intermediate transfer member with contacting the intermediate transfer member after a completion of the second transfer operation. The direct current voltage source applies a direct current voltage V to the discharging member to cause the discharging member to perform the discharging operation. The voltage detect sensor detects a surface voltage Va of the intermediate transfer member. The direct current voltage controller controls the direct current voltage V in a way such that the direct current voltage V relative to the surface voltage Va satisfies a range of
[xe2x88x921.3Vaxe2x88x92650# V #xe2x88x921.3va+550].
Further, the present application also relates to a method of image forming which includes the steps of providing, rotating, charge applying, performing, detecting, direct current voltage applying, and controlling. The providing step provides a toner image to an carrying member for rotating and carrying the toner image on a rotating surface thereof. The rotating step rotates an intermediate transfer member which is arranged at a position facing and in contact with the image carrying member. The applying step applies a charge to the intermediate transfer member to cause an electric field around a region where the image carrying member and the intermediate transfer member contact with each other so that the electric field generates a force for initiating a first transfer operation for transferring the toner image from the image carrying member to the intermediate transfer member. The performing step performs a second transfer operation for transferring the toner image from the intermediate transfer member to a transfer sheet. The detecting step detects a surface voltage Va of the intermediate transfer member. The applying step applies a direct current voltage V to the discharging member to cause the discharging member which discharges the charge remaining on the intermediate transfer member with contacting the intermediate transfer member after a completion of the second transfer operation. The controlling step controls the direct current voltage V in a way such that the direct current voltage V relative to the surface voltage Va satisfies a range of
[xe2x88x921.3Vaxe2x88x92650 # V #xe2x88x921.3va+550].
Further, the present application also relates to a novel image forming apparatus which includes an image carrying member, an intermediate transfer member, a charging member, a transfer mechanism, a discharging member, a direct current voltage source, a judging mechanism, and a direct current voltage controller. The image carrying member rotates and carries a toner image on a rotating surface thereof. The intermediate transfer member which is deposited at a position facing and in contact with the image carrying member, rotates and receives the toner image from the image carrying member during a first transfer operation which is performed for one time in a mono color mode and is repeated for a plurality of times in a multiple color mode to overlay a plurality of mono color toner images in turn on the intermediate transfer member. The charging member applies a charge to the intermediate transfer member to cause an electric field around a region where the image carrying member and the intermediate transfer member contact with each other, where the electric field generates a force for initiating the first transfer operation. The transfer mechanism performs a second transfer operation for transferring the toner image from the intermediate transfer member to a transfer sheet. The discharging member performs a discharging operation for discharging the charge remaining on the intermediate transfer member with contacting the intermediate transfer member after a completion of the second transfer operation. The direct current voltage source applies a direct current voltage to the discharging member to cause the discharging member to perform the discharging operation. The judging mechanism judges as to whether the apparatus is in the mono color mode or in the multiple color mode. The direct current voltage controller controls the direct current voltage in accordance with a result of judgement by the judging mechanism.
Further, the present application also relates to a novel method of image forming which includes providing, rotating, charge applying, performing, judging, direct current voltage applying, and controlling. The providing step provides a toner image to an carrying member for rotating and carrying the toner image on a rotating surface thereof. The rotating step rotates an intermediate transfer member which is arranged at a position facing and in contact with the image carrying member. The charge applying step applies a charge to the intermediate transfer member to cause an electric field around a region where the image carrying member and the intermediate transfer member contact with each other so that the electric field generates a force for initiating a first transfer operation for transferring the toner image from the image carrying member to the intermediate transfer member. The above-mentioned first transfer operation is performed for one time in a mono color mode and is repeated for a plurality of times in a multiple color mode to overlay a plurality of mono color toner images in turn on the intermediate transfer member. The performing step performs a second transfer operation for transferring the toner image from the intermediate transfer member to a transfer sheet. The judging step judges as to whether the apparatus is in the mono color mode or in the multiple color mode. The direct current voltage applying step applies a direct current voltage to the discharging member to cause the discharging member to discharge the charge remaining on the intermediate transfer member with contacting the intermediate transfer member after a completion of the second transfer operation. The controlling step controls the direct current voltage in accordance with a result of judgement by the judging mechanism.
Further, the present application also relates to a novel lubricant applying apparatus for applying a lubricant to an intermediate transfer member in an image forming apparatus. The above-mentioned novel lubricant applying apparatus includes a lubricant applying member for applying a lubricant to the intermediate transfer member and discharging a charge remaining on the intermediate transfer member.